Method of casting objects from magnesia cements



Patented Mar. 13, 1951 'Y U NITE' D FFICE METHoD. oFcAsTINGonino'rsivnoivr Jean Franc'oisfV Marie VerdierDufnum Barts, I'ranccr41511illrjawing.V Application August 3i, 1949,S`eriai N0. 1153,489L InFrance/'May 19,l

l It i's- Weir known that magnesiacements, pre pared from calci-ned"magnesiamixedz eventually' Withvmineral-ized or other llers and With-aSolu-r tion of magnesium salts, forV exam-ple magnesium chloride orsulphate, yield Very hard" superiicial``A ly'V bright castings Voi'considerablev mechanical strength. However; the dliiusion' oftheseproii-l ucts; namely by WayK of: casting; and their'industrialutilization are almost insignificant on ac-` count; of" difd'culty andtime involvedn in carrying out casting operation. The latterconsistsgfenerallyin feedinga more or less' liquid pasty mass into asuitable mold from'A which, however, the* casting may be removedonly'When the chemical reaction; causing the" setting, is sufficientlyadvanced to render the casting'suicient'ly' cohesive topermititsdischarge from the mold; this requirest a time'vvarying according tothe kinds ofmagnesial employed; its temperature; and time ofcaleination-elem'ent's generally unknown toV the,

melder, fillers added 'accord-ing' to bothtl'ieir natures andvproportions, surrounding atmospherie conditions (temperatures, humidity,etc.

rEhe-time thus` reduired'is at least severalhours-if" not sever-al days.It results therefrom that theretur-n of the-molds is` ver-y slow` anddiicultto organize ou account oi a great number `ofyariablesinfi-uencing the time-`y of stay in tii'ernolds3 and because or theVuncertainty in which` the molder'ndsf'himself? aste the exact numberloiagainst an easy stripping which is rendered still.

more difficult by frequent adherences of the mag- Y ne'sia lproductt'othe mold' body, adherences produced by multiple causes such aspenetration of the magnesia mass or its liquid component by capillarityinto a porous portion of the mold, or partial oxidation of ythe latterby oxychlorides or oxysulphates of magnesia, formed in the course ofsetting. This calls for molds of excessive capacity, hence sometimescomplicated and difficult to make. On the other hand, superficialrepairs on the castings are often necessary, after stripping, whichenhance the cost of manpower comme., (o1. 254155) and. yet remaingenerally visible since magnesia cement/after its setting has a colorpaler on its surface: than within: its mass, and this is all the more'Visible asthemassi'smore pigmented. The' last mentioned shortcoming maybeL remedied by coating-theisurface offri cast iuagn'esia object with"a= paintgor a varnish, aiter` the'mfanner of plaster' obiects,y butthisAannihilates the' aspect superiority ofthe magnesia ceinents over theplaster which;

f at' present, isl lessi costly, vmore expeditious and'- easi'er' tocast.

Furthermore; the magnesia castings thusl oltr-l tained are seldomstable, for theyare' subject tounforeseen -iiaws occurring therein evenseveral pieces.

In a more general way, the excess oimagnesia salt solution addedtoobtairr a fluidity' suf'cient for' thenurp'oseofL casting,remainsuncompound ed'an-d? owing to its hy'groseopicityfv either absorbsorA litera-tes the huinidity;y giving' rise to moist spots appearingsurreptitious'ly on the casta'rticles severall daysA after casting, orto whitisn deposits irregularlyv` altering the aspect of the articles: Y

' The present invention lias for/ its object toV proe- Vide aA simple'method-that permits, of remedyin'g" these'variousshortcomings and, at'the same time,

lowering the prime c'ostgoftcasting: This methodv consistssubstantiailyin subjecting a mixture of constituent elements of aforesaid magnesiacements vCmagnesia Mg, magnesia carbonate ll/IgQCOz, or a mixturethereof,y to whichM convenient fillers maybe added; ina solution of'v asalt of magnesium such for example as magnesiuin ,chioricu'efy orsulphate-i to a short-lasting pressure ina suitable' moid, andimmediately thereafterdischarging from this mold the casting; which,under' thea action orsaidpressure, has 'acquiredia siniicient cohesionpermitting the same toi bei discharged; and' manipulated', the chemicaltransformation, Whichhasforits elfe-ctY to harden. tnemajgnesiaproduct;. goingA on4 outside of the moldand ending in imparting' to thecasting the desired qualities inherent to the magnesia cements. The timeof this hardening is in the same order of magnitude as in the usualmethods, but since this hardening takes place outside of the mold, thelatter is not immobilized, While, on the other hand, the cohesionimparted to the casting by the pressure permits the same to bemanipulated, conditioned, forwarded, etc. only the actual use of thecasting should be made after this attains its total hardness; thelatter, however, is always obtained in a lapse of time practicallyshorter than that required according to the usual methods, account beingtaken of the time necessary for making-,the article and the time atwhich this article may.be set in actual service.

The present method therefore permits, without any inconvenience, ofrapidly discharging the casting from its mold within a predetermined andconstant lapse of time for a given pressure, in a mechanical and reallyindustrial way.

Furthermore, the castings made according to this method are alwaysstable, whatever maybe,

both in proportion and in nature, the additiont of ,timeA that may beinferior to 2 or3 ,minutes approximately. This lapse of time may be madeshorter by employing higher pressures: from 400 to 12,00 kg./cm.2; itwill even suii'ice to apply an instantaneous pressure such as thatobtained by means of high duty stamping or other presses. Thus, theremay be obtained a succession of castings at the rate of say from to 60pieces per minute, while a succession of molds and discharges, as longas suicient pressure is available, will be limited lto equipmentavailable for filling the molds.

l The same principle permits of working up pastes obtained from the sameelements, by causing them to pass through a suitable die after themanner used for coiling rubber containing materials.

Any molding methods may serve the purpose of the invention, inparticular those used for molding thermo-hardening or thermo-plasticresins, or metals under pressure. 'Ihe mold employed may be an open moldlike one used for resins, or a chill mold like one used for metals, orelse it may be composed of a stationary part having the proiileV of thepiece to be executed and in which there are arranged two slidingpistons, one being a presser and theV other an ejector, and whose'activesurfaces are exact negatives of each of the faces of the object to bemade; it is then desirable to have the pistonejector surface as large aspossible. Single or multiple molds may be used, with or without pins inwhich it is compressed say under effective pressure of 200 kg./cm.2 forfrom 1 to 2 minutes, or for a shorter time under a higher pressure. Atthe end of this compression the casting or castings have a sufcientcohesion to permit them to be immediately discharged (either by openingthe mold or by ejection, or in any other way) and manipulated, as may bedesired, without their edges being damaged thereby since theircompression in the mold has been suiliciently effective.

The invention permits, on one hand, of obtaining a return of the moldsemployed much more expeditious than that made possible by the existingmethods of casting magnesia cements, and even more expeditious than thatobtained in casting plastic materials such as synthetic resins,

and, on the other hand, of avoiding the Well cal and physical, forexample their incombustibility.` Moreover, the invention permits ofconsiderably reducing the cost of production, as compared with existingmethods.

The method of the invention may have applications toy casting all sortsof objects, such as lining and decoration articles, statuettes, toys,funeral articles, publicity objects, household articles, covers,handles, parts of electricalV and other industrial apparatus, etc., andin a general way a wide variety of articles having for their desiredqualities a low cost of production, accurate dimensions and similarity,great superficial hardness, rigidity, Vincombustibility,imputrescibility.

What is claimed is:

l. The method of casting in moulds, articles,

the pressure is within the range from V kit/Cm? to 20o ini/cm2 and theduration of the pressure in the range from 3 to 1 minutes.

3. The method as claimed in claim 1 wherein` the pressure is nearly 1200kil./cm.2 and-the duration of said pressure only one moment.

JEAN FRANCOIS MARIE VERDIER DUFOUR.

VREFERENCES CITED The following references are of record in the le ofthis patent:

UNITED STATES PATENTS Number Name Date Frosell Feb. 9, 1926'

